The invention relates to waterborne surface craft in the form of trimarans, i.e. having a main hull and two auxiliary hulls or floats (referred to hereinafter simply as floats) oppositely spaced from the main hull.
Such craft are often built as sailing craft and are noted for the high degree of stability they have in normal sailing attitudes due to the presence of the floats, In a state of capsize, however, the floats are a hindrance, making it more difficult to right the craft.
It is known to arrange that the floats of a trimaran can be lowered relative to the main hull for obtaining a more stable mooring configuration, the floats then simply resting freely on the water surface. Additionally, provision is sometimes made for retraction of the floats of a trimaran, in order to reduce the beam of the craft for road-trailing. As an example, the Piver "Nugget" trimaran is a design that has floats connected to the main hull by longitudinally extending pivots, expressly for the purpose of trailing the craft more conveniently, and a similar arrangement has been provided in the "Tees Clipper" of J. Shewell & Co. Ltd. (Motor Boat and Yachting, Apr. 16, 1971, p. 70). Another example, the "Ocean Bird" design of Honnor Marine Ltd. (Yachting Monthly, December 1966, p. 323) has floats each mounted on a pair of parallel links with vertical pivot axis so that they are displaced fore and aft as they move between extended and retracted positions.
In such designs the retraction of the floats is not intended to be performed while the vessel is underway, and indeed in many instances it can be carried out only when the vessel has been hauled out of the water and onto its trailer. The retraction of the floats and securing them in place is thus invariably performed manually and cannot be done with any degree of safety or convenience, if at all, by the crew in their sailing positions while the vessel is underway.
It has been proposed to provide a proa (i.e. a craft with a single outrigger float) with emergency self-righting capability in the event of capsize by connecting the arms of the float to the main hull by drop-in pins that are held in place simply by gravity. In the event of the craft being completely capsized the pins will drop out and the float is detached. In such conditions the crew cannot be relied on to retrieve and re-secure the float while righting the craft and the main hull must be so designed and provided with a ballast keel that it can be sailed without the float (Yachting World, September 1967, pp 416-418). The arrangement thus clearly does not allow for the float to be locked again in its extended position while the craft is underway, particularly if sailing in rough water as is most likely if a capsize has occurred and when the detached float will probably be irretrievable, and is thus simply an emergency measure. Nor is the arrangement capable of stabilising the craft in any condition other than complete capsize since the pins will only fall out when the craft has overturned. Moreover, although the release of the floats in such a condition is necessarily arranged to occur automatically, if it failed to operate it would be impossible for the release to be effected manually while the craft is underway.
It is an object of the present invention to provide means for retraction and extension of the floats of a trimaran that can be utilised while the vessel is underway.
It is another object of the invention to provide retraction means that are operated automatically in dependence upon the heel of the craft, whereby correction of an unstable situatioin can be initiated at an early stage without relying on action by the crew.
It is a further object of the invention to provide means whereby such automatic retraction of the floats can be overriden simply and effectively by the crew whereby to permit them to exercise control of this function while the craft is underway, if they judge it to be desirable.